A Study Of Chattering Elimination In Sliding Mode Control System

Sliding mode control (SMC) is becoming an important branch of modern control theory. It is valued for its robust accommodation of uncertainties and its ability to reject disturbances. However, there is a gap between the sliding mode control theory and the application in real word. An ideal sliding mode does not exist in practice since it would imply that the control commutes at an infinite frequency. In the presence of switching imperfections, it is impossible for the control to commute at an infinite frequency. So, the discontinuity in the feedback control produces a particular dynamic behavior in the vicinity of the surface, which is commonly referred to as chattering.How to eliminate the chattering phenomenon while keeping the robustness property of SMC is the most important problem to be resolved for its wide application. This problem is studied in this dissertation. The main contents are as following:1. Based on refering to comaparaively full literatures in the field of VSC, the development history and research status of VSC are summarized, and the elementary concepts, elementary properties and design methods are particularly introduced.2. The SMC system is designed, and the main property of SMC system is analysized by some simulations. The invariance property of SMC and its matching condition are discussed by some simulations comparing with the conventional optimal control system (bang-bang control system). The causes of the chattering phenomenon are systematically analyzed, and the study status of the chattering phenomenon and the main methods to eliminate chattering are elaborated, at the same time the advantages and disadvantages of these methods are pointed out.3. The higher-order sliding mode control (HOSM) theory is stated, and the reasons why HOSM can eliminate chattering are explained. Some second order sliding mode controllers and the construction of arbitrary order sliding mode controllers are elaborated. The boundary layer SMC system, second-order and third-order SMC systems are designed, and some simulations are done on them to analyze the validity and limitation of these mehotds to eliminate the chattering phenomenon.4. On the basis of the concept of HOSM, a new arbitrary-order sliding mode controller for the plants involved with actuators is designed. While keeping the main advantages of standard sliding mode control, it totally removes the chattering effect. Some simulations on...